Optimal Solution to Multi-Frequency BDS Code-Multipath Combination Measurement

2019 ◽  
Vol 72 (5) ◽  
pp. 1297-1314
Author(s):  
Tian Jin ◽  
Bingjie Hu ◽  
Yining Sun ◽  
Zhigang Huang ◽  
Qian Wang ◽  
...  
Keyword(s):  
Rapid Development ◽  
Optimal Solution ◽  
Satellite System ◽  
Frequency Data ◽  
International Gnss Service ◽  
Triple Frequency ◽  
Multipath Combination ◽  
Beidou System ◽  
Global Navigation Satellite ◽  
Gnss Observations

Global Navigation Satellite System (GNSS) observations contain various errors, the separation and measurement of which is a popular research topic. Multipath effect on code measurements is investigated through the multipath combination, but carrier multipath error is small, and it is difficult to distinguish from other errors, such as hardware delay, carrier noise and satellite inherent biases. However, as the number of frequency points increases during the rapid development of GNSSs, it is possible to analyse the abovementioned errors in detail. Triple-frequency combination can be used to eliminate the first order ionospheric error, and a quad-frequency combination has one degree of freedom, which may be used to minimise carrier error effects. For this reason, an optimum method has been developed for multi-frequency GNSS code-multipath combination measurements, which has been verified by exploiting BeiDou System (BDS), three frequency data from an International GNSS Service (IGS) station and a city canyon as well as actual sampled quad-frequency data. By comparative analysis, we found that the fluctuations of an optimum triple-frequency combination are smaller than that of the non-optimum combination, which decreases the influence of inherent errors and biases on carrier phase. At the same time, second-order ionospheric error can be effectively eliminated as well. This provides a new code-multipath combination measurement optimisation methodology for future multi-frequency BDS and other GNSSs.

scholarly journals Validating HY-2A CMR precipitable water vapor using ground-based and shipborne GNSS observations

2020 ◽  
Vol 13 (9) ◽  
pp. 4963-4972
Author(s):  
Zhilu Wu ◽  
Yanxiong Liu ◽  
Yang Liu ◽  
Jungang Wang ◽  
Xiufeng He ◽  
...  
Keyword(s):  
Water Vapor ◽  
Microwave Radiometer ◽  
Precipitable Water ◽  
Satellite System ◽  
Precipitable Water Vapor ◽  
Tropospheric Delay ◽  
High Temporal Resolution ◽  
International Gnss Service ◽  
Global Navigation Satellite ◽  
Gnss Observations

Abstract. The calibration microwave radiometer (CMR) on board the Haiyang-2A (HY-2A) satellite provides wet tropospheric delay correction for altimetry data, which can also contribute to the understanding of climate system and weather processes. The ground-based global navigation satellite system (GNSS) provides precise precipitable water vapor (PWV) with high temporal resolution and could be used for calibration and monitoring of the CMR data, and shipborne GNSS provides accurate PWV over open oceans, which can be directly compared with uncontaminated CMR data. In this study, the HY-2A CMR water vapor product is validated using ground-based GNSS observations of 100 International GNSS Service (IGS) stations along the global coastline and 56 d shipborne GNSS observations over the Indian Ocean. The processing strategy for GNSS data and CMR data is discussed in detail. Special efforts were made in the quality control and reconstruction of contaminated CMR data. The validation result shows that HY-2A CMR PWV agrees well with ground-based GNSS PWV with 2.67 mm as the root mean square (rms) within 100 km. Geographically, the rms is 1.12 mm in the polar region and 2.78 mm elsewhere. The PWV agreement between HY-2A and shipborne GNSS shows a significant correlation with the distance between the ship and the satellite footprint, with an rms of 1.57 mm for the distance threshold of 100 km. Ground-based GNSS and shipborne GNSS agree with HY-2A CMR well.

Ionosphere VTEC modeling with the raw-observation-based PPP model：an advantage demonstration in the multi-frequency and multi-GNSS context

2020 ◽  
Author(s):  
Teng Liu ◽  
Baocheng Zhang ◽  
Yunbin Yuan ◽  
Xiao Zhang
Keyword(s):  
Rapid Development ◽  
Global Navigation Satellite Systems ◽  
Electron Content ◽  
Vertical Total Electron Content ◽  
Dual Frequency ◽  
International Gnss Service ◽  
Total Electron ◽  
Satellite Systems ◽  
Triple Frequency ◽  
Global Navigation Satellite

<p>The ionospheric delay accounts for one of the major errors that the Global Navigation Satellite Systems (GNSS) suffer from. Hence, the ionosphere Vertical Total Electron Content (VTEC) map has been an important atmospheric product within the International GNSS Service (IGS) since its early establishment. In this contribution, an enhanced method has been proposed for the modeling of the ionosphere VTECs. Firstly, to cope with the rapid development of the newly-established Galileo and BeiDou constellations in recent years, we extend the current dual-system (GPS/GLONASS) solution to a quad-system (GPS/GLONASS/Galileo/BeiDou) solution. More importantly, instead of using dual-frequency observations based on the Carrier-to-Code Leveling (CCL) method, all available triple-frequency signals are utilized with a general raw-observation-based multi-frequency Precise Point Positioning (PPP) model, which can process dual-, triple- or even arbitrary-frequency observations compatibly and flexibly. Benefiting from this, quad-system slant ionospheric delays can be retrieved based on multi-frequency observations in a more flexible, accurate and reliable way. The PPP model has been applied in both post-processing global and real-time regional VTEC modeling. Results indicate that with the improved slant ionospheric delays, the corresponding VTEC models are also improved, comparing with the traditional CCL method.</p>

scholarly journals Assessment of GNSS PPP-Based Zenith Tropospheric Delay

2020 ◽  
Vol 55 (4) ◽  
pp. 171-184
Author(s):  
Mohamed Abdelazeem ◽  
Ahmed El-Rabbany
Keyword(s):  
Precise Point Positioning ◽  
Satellite System ◽  
Tropospheric Delay ◽  
International Gnss Service ◽  
Zenith Tropospheric Delay ◽  
Global Navigation Satellite ◽  
The University ◽  
Globally Distributed ◽  
By Products ◽  
Gnss Observations

AbstractThis study assesses the precision of zenith tropospheric delay (ZTD) obtained through triple-constellation global navigation satellite system (GNSS) precise point positioning (PPP). Various ZTD estimates are obtained as by-products from GPS-only, GPS/Galileo, GPS/BeiDou, and triple-constellation GPS/Galileo/BeiDou PPP solutions. Triple-constellation GNSS observations from a number of globally distributed reference stations are processed over a period of seven days in order to investigate the daily performance of the ZTD estimates. The estimated ZTDs are then validated by comparing them with the International GNSS Service (IGS) tropospheric products and the University of New Brunswick (UNB3m) model counterparts. It is shown that the ZTD estimates agree with the IGS counterparts with a maximum standard deviation (STD) of 2.4 cm. It is also shown that the precision of estimated ZTD from the GPS/Galileo and GPS/Galileo/BeiDou PPP solutions is improved by about 4.5 and 14%, respectively, with respect to the GPS-only PPP solution. Moreover, it is found that the estimated ZTD agrees with the UNB3m model with a maximum STD of 3.1 cm. Furthermore, the GPS/Galileo and GPS/Galileo/BeiDou PPP enhance the precision of the ZTD estimates by about 6.5 and 10%, respectively, in comparison with the GPS-only PPP solution.

On the Feasibility and Applicability of Multipath Mitigation Maps as an IGS Product

2020 ◽  
Author(s):  
Addisu Hunegnaw ◽  
Yohannes Getachew Ejigu ◽  
Felix Norman Teferle ◽  
Gunnar Elgered
Keyword(s):  
Carrier Phase ◽  
Satellite System ◽  
Screening Tests ◽  
International Gnss Service ◽  
Multipath Mitigation ◽  
Harmonic Signals ◽  
The One ◽  
Global Navigation Satellite ◽  
Gnss Observations

<p>Multipath is a largely unmodelled source of error and causes large range errors in Global Navigation Satellite System (GNSS) observations. The effects have strong site-specific characteristics and impact each receiver differently. Multipath errors can propagate and can cause in-situ position and velocity biases and are also contributing to the pervasive draconitic harmonic signals. We employ an empirical approach to reducing the effects of multipath by stacking one-way post-fit carrier phase residual observations by applying an appropriate averaging scheme. Our processing is based on static multi-GNSS observations using various scientific GNSS software packages (Bernese GNSS Software, NAPEOS, GAMIT-GLOBK, PRIDE and GINS). Our multipath stacking (MPS ) uses the stacking of individual residuals generated by variable azimuth cell size (congruent cells) by allocating carrier phase residuals in each cell, unlike fixed azimuth cell resolution in the standard MPS approaches. This reduces the binning of fewer residuals at higher elevation angles. Before stacking, we also apply rigorous statistical outlier screening tests for each one-way post-fit carrier phase residual assigned to each of the congruent cells. We thus correct the multipath effects by subtracting the stacked multipath map from the post-fit carrier phase residual. Using this technique we produce a model available in the form of the Antenna Exchange (ANTEX) file format, that can potentially be implemented in routine GNSS analysis with no or little additional overhead for individual analysis centers (ACs).</p><p>In this study, we assess the feasibility and applicability of the MPS maps as an International GNSS Service (IGS) product for routine GNSS analysis. We have selected a subset of IGS stations with and without known multipath issues in different climatic zones. We demonstrate the multipath stacking technique to result in a significant reduction of the variation in the one-way post-fit carrier phase residuals. For GPS-only solutions, the MPS technique shows a decrease of up to 30% in the RMS value of the one-way post-fit carrier phase residuals. We have also tested our MPS for other constellations such as GLONASS, Galileo and BeiDou, and combinations of these .</p>

scholarly journals Characterization of multi-scale ionospheric irregularities using ground-based and space-based GNSS observations

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
YuXiang Peng ◽  
Wayne A Scales ◽  
Michael D Hartinger ◽  
Zhonghua Xu ◽  
Shane Coyle
Keyword(s):  
Formation Flying ◽  
Satellite System ◽  
Ionospheric Irregularities ◽  
Mission Design ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Scales ◽  
Multi Scale ◽  
Global Navigation Satellite ◽  
Gnss Observations

AbstractIonospheric irregularities can adversely affect the performance of Global Navigation Satellite System (GNSS). However, this opens the possibility of using GNSS as an effective ionospheric remote sensing tool. Despite ionospheric monitoring has been undertaken for decades, these irregularities in multiple spatial and temporal scales are still not fully understood. This paper reviews Virginia Tech’s recent studies on multi-scale ionospheric irregularities using ground-based and space-based GNSS observations. First, the relevant background of ionospheric irregularities and their impact on GNSS signals is reviewed. Next, three topics of ground-based observations of ionospheric irregularities for which GNSS and other ground-based techniques are used simultaneously are reviewed. Both passive and active measurements in high-latitude regions are covered. Modelling and observations in mid-latitude regions are considered as well. Emphasis is placed on the increased capability of assessing the multi-scale nature of ionospheric irregularities using other traditional techniques (e.g., radar, magnetometer, high frequency receivers) as well as GNSS observations (e.g., Total-Electron-Content or TEC, scintillation). Besides ground-based observations, recent advances in GNSS space-based ionospheric measurements are briefly reviewed. Finally, a new space-based ionospheric observation technique using GNSS-based spacecraft formation flying and a differential TEC method is demonstrated using the newly developed Virginia Tech Formation Flying Testbed (VTFFTB). Based on multi-constellation multi-band GNSS, the VTFFTB has been developed into a hardware-in-the-loop simulation testbed with external high-fidelity global ionospheric model(s) for 3-satellite formation flying, which can potentially be used for new multi-scale ionospheric measurement mission design.

scholarly journals Investigation of GIM-TEC disturbances before M ≥ 6.0 inland earthquakes during 2003–2017

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fuying Zhu ◽  
Yingchun Jiang
Keyword(s):  
Rapid Development ◽  
Science Research ◽  
Satellite System ◽  
Statistical Investigation ◽  
Electron Content ◽  
Total Electron ◽  
Spatial And Temporal Distributions ◽  
Before And After ◽  
Global Ionosphere Map ◽  
Global Navigation Satellite

Abstract With the rapid development of the Global Navigation Satellite System (GNSS) and its wide applications to atmospheric science research, the global ionosphere map (GIM) total electron content (TEC) data are extensively used as a potential tool to detect ionospheric disturbances related to seismic activity and they are frequently used to statistically study the relation between the ionosphere and earthquakes (EQs). Indeed, due to the distribution of ground based GPS receivers is very sparse or absent in large areas of ocean, the GIM-TEC data over oceans are results of interpolation between stations and extrapolation in both space and time, and therefore, they are not suitable for studying the marine EQs. In this paper, based on the GIM-TEC data, a statistical investigation of ionospheric TEC variations of 15 days before and after the 276 M ≥ 6.0 inland EQs is undertaken. After eliminating the interference of geomagnetic activities, the spatial and temporal distributions of the ionospheric TEC disturbances before and after the EQs are investigated and compared. There are no particularly distinct features in the time distribution of the ionospheric TEC disturbances before the inland EQs. However, there are some differences in the spatial distribution, and the biggest difference is precisely in the epicenter area. On the other hand, the occurrence rates of ionospheric TEC disturbances within 5 days before the EQs are overall higher than those after EQs, in addition both of them slightly increase with the earthquake magnitude. These results suggest that the anomalous variations of the GIM-TEC before the EQs might be related to the seismic activities.

scholarly journals Centro de Análise Sirgas - IBGE: novas estratégias de processamento e combinação, e a influência da mudança do referencial global nos resultados

2012 ◽  
Vol 18 (1) ◽  
pp. 63-85
Author(s):  
Sonia Maria Alves Costa ◽  
Alberto Luis Da Silva ◽  
Marco Aurélio De Almeida Lima ◽  
Newton José De Moura Júnior
Keyword(s):  
Global Navigation Satellite System ◽  
Satellite System ◽  
Navigation Satellite ◽  
International Gnss Service ◽  
Global Navigation ◽  
Global Navigation Satellite

Atualmente, o SIRGAS (Sistema de Referência Geocêntrico para as Américas) é realizado por uma rede GNSS (Global Navigation Satellite System) permanente denominada SIRGAS-CON, com cerca de 240 estações em funcionamento permanente, distribuídas na América do Sul, Central e Caribe. Os Centros de Análise SIRGAS foram estabelecidos com a finalidade de determinar sistematicamente as coordenadas das estações SIRGAS-CON, seguindo padrões estabelecidos internacionalmente, a fim de apoiar a manutenção do sistema e as atividades do Grupo de Trabalho SIRGAS-GT I (Sistema de Referência). Desde agosto de 2008 a Coordenação de Geodésia do Instituto Brasileiro de Geografia e Estatística-IBGE assumiu oficialmente as atividades de um Centro de Análise. Este é um trabalho cuja dedicação é crescente uma vez que o número de estações no continente Sul Americano vem aumentando rapidamente nos últimos anos. Desta atividade diária são geradas dentre outros resultados, as séries temporais das coordenadas de cada estação, possibilitando assim a determinação dos deslocamentos das estações em função da movimentação da crosta terrestre, os movimentos locais como subsidência e/ou soerguimento crustal, causados por fenômenos naturais, como por exemplo, terremotos, além de efeitos sazonais causados por fatores diversos. Paralelamente a atividade de processamento dos dados GNSS, o IBGE também realiza semanalmente a combinação das soluções semanais dos nove Centros de Processamento SIRGAS. Esta combinação tem por objetivo comparar os resultados com os obtidos pelo DGFI (Deutsches Geodätisches Forschungsinstitut), o qual disponibiliza a solução final semanal da rede SIRGAS-CON. Por se tratar de resultados precisos, a mudança em alguma informação no processamento pode acarretar alterações nas coordenadas determinadas e, conseqüentemente, descontinuidades nas séries temporais de cada estação. Recentemente, em 17 de abril de 2011 (semana GPS 1632), as órbitas (finais e rápidas), as correções dos relógios dos satélites e o modelo de calibração das antenas disponibilizado pelo International GNSS Service - IGS, passaram a estar referidos à nova realização do IGS, denominada IGS08. Conseqüentemente, a partir dessa data, os processamentos GPS que utilizam os produtos IGS terão seus resultados referidos a este novo sistema de referência, o que poderá acarretar descontinuidades nas coordenadas. O objetivo desse trabalho é apresentar a estratégia de processamento atualmente em operação, bem com uma nova estratégia visando à melhoria dos resultados. Outro objetivo é apresentar alguns resultados do processamento e combinação semanal realizados pelo IBGE, bem como esclarecer as alterações ocorridas com a adoção da nova versão da Rede de Referência Global para soluções GNSS, o IGS08 e uma análise preliminar da conseqüência desta mudança.

scholarly journals Kinematic PPP Using Mixed GPS/Glonass Single-Frequency Observations

2019 ◽  
Vol 54 (3) ◽  
pp. 97-112
Author(s):  
Mostafa Hamed ◽  
Ashraf Abdallah ◽  
Ashraf Farah
Keyword(s):  
Low Cost ◽  
Satellite System ◽  
Single Frequency ◽  
Future Research ◽  
Frequency Data ◽  
Dual Frequency ◽  
Trajectory Data ◽  
Average Improvement ◽  
Kinematic Ppp ◽  
Global Navigation Satellite

Abstract Nowadays, Precise Point Positioning (PPP) is a very popular technique for Global Navigation Satellite System (GNSS) positioning. The advantage of PPP is its low cost as well as no distance limitation when compared with the differential technique. Single-frequency receivers have the advantage of cost effectiveness when compared with the expensive dual-frequency receivers, but the ionosphere error makes a difficulty to be completely mitigated. This research aims to assess the effect of using observations from both GPS and GLONASS constellations in comparison with GPS only for kinematic purposes using single-frequency observations. Six days of the year 2018 with single-frequency data for the Ethiopian IGS station named “ADIS” were processed epoch by epoch for 24 hours once with GPS-only observations and another with GPS/GLONASS observations. In addition to “ADIS” station, a kinematic track in the New Aswan City, Aswan, Egypt, has been observed using Leica GS15, geodetic type, dual-frequency, GPS/GLONASS GNSS receiver and single-frequency data have been processed. Net_Diff software was used for processing all the data. The results have been compared with a reference solution. Adding GLONASS satellites significantly improved the satellite number and Position Dilution Of Precision (PDOP) value and accordingly improved the accuracy of positioning. In the case of “ADIS” data, the 3D Root Mean Square Error (RMSE) ranged between 0.273 and 0.816 m for GPS only and improved to a range from 0.256 to 0.550 m for GPS/GLONASS for the 6 processed days. An average improvement ratio of 24%, 29%, 30%, and 29% in the east, north, height, and 3D position components, respectively, was achieved. For the kinematic trajectory, the 3D position RMSE improved from 0.733 m for GPS only to 0.638 m for GPS/GLONASS. The improvement ratios were 7%, 5%, 28%, and 13% in the east, north, height, and 3D position components, respectively, for the kinematic trajectory data. This opens the way to add observations from the other two constellations (Galileo and BeiDou) for more accuracy in future research.

scholarly journals Determination of Conversion Constant between Lagos Datum and Niger Delta Mean Lower Low Water Datum and their Horizontal and Vertical Accuracy Standards using GNSS Observations

2018 ◽  
Vol 2 (1) ◽  
pp. 56-68
Author(s):  
M. O. Ehigiator ◽  
S. O. Oladosu
Keyword(s):  
Niger Delta ◽  
Satellite System ◽  
Constant Factor ◽  
Common Mean ◽  
Height Determination ◽  
The Mean ◽  
Vertical Accuracy ◽  
Global Navigation Satellite ◽  
Gnss Observations

With the use of Global Navigation Satellite System (GNSS) technology, it is now possible to determine the position of points in 3D coordinates systems. Lagos datum is the most common Mean Sea Level used in most parts of Nigeria. In Niger Delta, for instance Warri and its environs, the most commonly used datum for height determination is the Mean Lower Low Water Datum. It then becomes necessary to determine a constant factor for conversion between the two datum when the need arises as both are often encountered during Geomatics Engineering field operations. In this paper, the constant to be applied in converting between both datum was determined. The constant was found to be 17.79m. The horizontal and vertical accuracy standard was also determined as well as the stack maps.

scholarly journals GNSS brings us back on the ground from ionosphere

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Yang-Yi Sun
Keyword(s):  
Solar Eclipse ◽  
Southern Oscillation ◽  
Walker Circulation ◽  
Satellite System ◽  
Total Solar Eclipse ◽  
Navigation Satellite ◽  
Terrestrial Environment ◽  
Global Navigation Satellite ◽  
Gnss Observations ◽  
Complicated Nature

AbstractBoth solar activities from above and perturbations of Earth’s surface and troposphere from below disturb ionospheric structure and its dynamics. Numerous ionospheric phenomena remain unexplained due to the complicated nature of the solar–terrestrial environment. We do appreciate the ground- and space-based Global Navigation Satellite System (GNSS) techniques being around and providing global observations with high resolutions to help us to resolve unexplained phenomena. This paper summarizes recent studies of the effect of solar (geomagnetic storm and total solar eclipse), tropospheric (typhoon, walker circulation, and El Niño-Southern Oscillation), and earthquake/tsunami activities (2010 Chile, 2011 Tohoku, and 2015 Nepal earthquakes) on the ionosphere utilizing the global ground- and space-based GNSS observations.

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